A conventional automatic vehicle-body assembling apparatus of the nature above specified is composed solely of a number of multi-spot welding machines arranged along an assembly line. Each of these welding machines includes positioning means adapted to hold together a plurality of component assemblies to constitute a vehicle floor structure and jig units including spot welding heads for spot welding together the component assemblies thus positioned with respect to each other. In this instance, the jig units are arranged so that the welding heads are operative to have the component assemblies of the vehicle floor structure spot welded simultaneously at a number of locations of the component assemblies. The jig units of the welding machine are designed depending upon the types, models and/or makes of the automotive vehicles to be manufactured and, for this reason, must be utilized for the assembling of vehicle floor structures of a single specified type, model or make. When the automotive vehicles to be supplied from an automotive manufacturer are to be re-modelled or modified in type or make, therefore, the existing assembly line which has been put to use sometimes becomes useless so that it may be required for the automotive manufacturer to have the existing assembly line supplanted by an up-to-date version of the assembly line or shut down for an extended period of time until the jig units which have been used in the obsolete assembly line are completely exchanged with new ones. Problems have therefore been encountered in that a vast amount of investment is required on the part of the manufacturer or in that the labor and production equipment are wasted for a long period of time.
To save the production costs of automotive vehicles, on the other hand, attempts are being made in the automotive industry to assemble vehicle bodies of different models, types and/makes in a single assembly line. One of such attempts is taught in the applicants ' copending Japanese Patent Application Publication No. 54-103,755 dated Aug. 15, 1979. In this patent application, a welding machine is disclosed having jig or fixture assemblies which can be easily exchanged with other ones depending upon the models, types and/or makes of the vehicle bodies to be assembled. In the improved version of assembling systems, however, the jig or fixture assemblies to be put to use for assembling a body structure for an automotive vehicle of one model, type or make are brought into operative positions thereof by means of manipulative means which differ from the manipulative means by which the jig or fixture assemblies are to be handled. Limitations have therefore been encountered in exchanging between the two or more manipulative means quickly and efficiently.
The present invention contemplates elimination of these problems by provision of an improved automatic vehicle body welding apparatus.